This invention is related to packings for geothermal wellheads. More particularly the invention is related to packing assemblies which are mounted on the casing and positioned inside the bore of a geothermal wellhead to seal the casing as it moves up and down in response to thermal conditions at the wellhead. In the construction of geothermal wells a casing is cemented in place in the hole extending from above the ground surface to the steam production zone, and a surface casing is cemented through the water bearing formation to the surface where the geothermal type wellhead is mounted. The casing is cemented in place to within a few feet of the ground surface so that is is substantially rigidly placed in the well. During periods when steam is passed through the casing it is heated and expands so the upper end of the casing above the cement level moves upward as its temperature raises. The distance which the casing moves upward depends upon the size of the casing and the distance from the top of the cement to the upper end of the casing. In conventional oil and gas wells the casing is secured in the wellhead by slips which support part or all of the weight of the casing. However, these devices will not function properly for geothermal wells because of expansion and contraction of the casing in the upper portion of the well. Heretofore geothermal wellhead structures are adaptations of conventional oil and gas wellheads wherein packing for the casing is mounted with the wellhead structure and seals on the exterior of the casing as it moves up and down. A basic fault in these prior art devices is the seal structures which they have are not constructed to provide effective sealing in the high temperature conditions and considering motion of the casing. Basically, the prior art devices have a seal mounted in the wellhead which rubs on the casing. This seal is urged against the casing by a plurality of screws which must be manually tightened and adjusted to seal the casing. In use of these devices motion of the casing loosens the seal thus necessitating readjusting the screws manually to tighten the seal. Another fault of the prior art devices is they do not have any provision for lubrication of the joint between the casing and the seal. One additional shortcoming of prior art devices is that they do not have anything to function as a corrosion inhibitor for metals inside the wellhead. Both corrosion and lubrication are factors which greatly affect seal life and performance in a geothermal wellhead because of the temperatures and elements involved.